The effect of natural and synthetic D-fructose 2,6-bisphosphate on the regulatory kinetic properties of liver and muscle phosphofructokinases.
The effect of natural and synthetic D-fructose 2,6-bisphosphate on the regulatory kinetic properties of liver and muscle phosphofructokinases.
复制标题
DOI：
--
复制
发表时间：
1981-08
期刊：
影响因子：
--
通讯作者：
K. Uyeda;Eisuke Furuya;Lynne J. Luby
中科院分区：
文献类型：
--
作者：
K. Uyeda;Eisuke Furuya;Lynne J. Luby
研究了天然“激活因子”和合成果糖-2，6-P2对肝和肌肉磷酸果糖激酶变构动力学性质的影响。合成和天然果糖-2，6-P2对两种酶的变构动力学性质显示出相同的影响。果糖-2，6-P2抵消ATP和柠檬酸盐的抑制作用，并降低果糖-6-P的Km。这种果糖酯还与AMP协同作用，释放ATP抑制作用。在1.25 mM ATP存在下，肝脏和肌肉磷酸果糖激酶对果糖-2，6-P2的Km值分别为12毫单位/ml（或24 nM）和5毫单位/ml（或10 nM）。然而，在接近生理浓度的ATP（3 mM）和果糖-6-P（0.2 mM）下，果糖-2，6-P2的Km值对于肝酶和肌肉酶分别增加到12 μ M和0.8 μ M。因此，与其他已知的激活剂如果糖-1，6-P2相比，果糖-2，6-P2是该酶的最有效的激活剂。在上述条件下，酶催化的反应速率是非线性的：在不存在或存在较低浓度的果糖-2，6-P2的情况下，速率减慢，但在存在较高浓度的果糖-2，6-P2的情况下，速率变为线性。果糖-2，6-P2也保护磷酸果糖激酶免受热灭活。因此，果糖-2，6-P2可能是调节肝脏以及其他组织中磷酸果糖激酶的最重要的变构效应物。
The effect of natural "activation factor" and synthetic fructose-2,6-P2 on the allosteric kinetic properties of liver and muscle phosphofructokinases was investigated. Both synthetic and natural fructose-2,6-P2 show identical effects on the allosteric kinetic properties of both enzymes. Fructose-2,6-P2 counteracts inhibition by ATP and citrate and decreases the Km for fructose-6-P. This fructose ester also acts synergistically with AMP in releasing ATP inhibition. The Km values of liver and muscle phosphofructokinase for fructose-2,6-P2 in the presence of 1.25 mM ATP are 12 milliunits/ml (or 24 nM) and 5 milliunits/ml (or 10 nM), respectively. At near physiological concentrations of ATP (3 mM) and fructose-6-P (0.2 mM), however, the Km values for fructose-2,6-P2 are increased to 12 microM and 0.8 microM for liver and muscle enzymes, respectively. Thus, fructose-2,6-P2 is the most potent activator of the enzyme compared to other known activators such as fructose-1,6-P2. The rates of the reaction catalyzed by the enzymes under the above conditions are nonlinear: the rates decelerate in the absence or in the presence of lower concentrations of fructose-2,6-P2, but the rates become linear in the presence of higher concentrations of fructose-2,6-P2. Fructose-2,6-P2 also protects phosphofructokinase against inactivation by heat. Fructose-2,6-P2, therefore, may be the most important allosteric effector in regulation of phosphofructokinase in liver as well as in other tissues.